Architectural lighting is designed to serve both practical and aesthetic goals. Lighting designers use natural light and a wide variety of illumination devices and surface finishes to achieve desired effects. For example, strings of lights are frequently employed to frame the edges of a building. With modern LED-based fixtures, it is easy to control brightness as well as color. For more exotic effects, video projectors can be employed to project dynamic images onto surfaces.
Current architectural lighting fixtures fall into one of two groups: direct view or indirect view. As the name implies, direct-view lighting is viewed directly by a viewer; that is, the viewer views the light source. Most direct-view lighting is designed to transmit light fairly uniformly in all directions. An example of direct-view lighting is a string of holiday lights. With indirect-view lighting, the viewer generally does not directly view the light source; rather, the viewer views light that has been scattered off a surface or passed through a diffusing material.
There is at least one significant limitation as to what can be achieved with either of the aforementioned lighting systems. Namely, any and all viewers that view the lighting effect at the same time share the same lighting experience. There is little ability to create different lighting experiences for different viewers.
In particular, consider direct view lighting. Although there might be different color bulbs in the string, any given light bulb in the string appears to be substantially the same color and brightness independent of a viewer's location with respect to the bulb. Likewise, with indirect-view lighting, the scattered or diffused light appears relatively uniform regardless of the location of the viewer.